The present invention relates to network interfacing, and more particularly, to methods and systems for controlling transmission of data between network stations connected to a telephone line medium.
Local area networks use a network cable or other media to link stations on the network. Each local area network architecture uses a media access control (MAC) enabling network interface cards at each station to share access to the media.
Conventional local area network architectures use media access controllers operating according to half-duplex or full duplex Ethernet (ANSI/IEEE standard 802.3) protocol using a prescribed network medium, such as 10 BASE-T. Newer operating systems require that a network station to be able to detect the presence of the network. In an Ethernet 10 BASE-T environment, the network is detected by the transmission of a link pulse by the physical layer (PHY) transceiver. The periodic link pulse on the 10 BASE-T media is detected by a PHY receiver, which determines the presence of another network station transmitting on the network medium based on detection of the periodic link pulses. Hence, a PHY transceiver at Station A is able to detect the presence of Station B, without the transmission or reception of data packets, by the reception of link pulses on the 10 BASE-T medium from the PHY transmitter at Station B.
Efforts are underway to develop an architecture that enables computers to be linked together using conventional twisted pair telephone lines instead of established local area network media such as 10 BASE-T. Such an arrangement, referred to herein as a home network environment, provides the advantage that existing telephone wiring in a home may be used to implement a home network environment. However, telephone lines are inherently noisy due to spurious noise caused by electrical devices in the home, for example dimmer switches, transformers of home appliances, etc. In addition, the twisted pair telephone lines suffer from turn-on transients due to on-hook and off-hook and noise pulses from the standard POTS telephones, and electrical systems such as heating and air conditioning systems, etc.
An additional problem in telephone wiring networks is that the signal condition (i.e., shape) of a transmitted waveform depends largely on the wiring topology. Numerous branch connections in the twisted pair telephone line medium, as well as the different associated lengths of the branch connections, may cause multiple signal reflections on a transmitted network signal. Telephone wiring topology may cause the network signal from one network station to have a peak-to-peak voltage on the order of 10 to 20 millivolts, whereas network signals from another network station may have a value on the order of one to two volts. Hence, the amplitude and shape of a received pulse may be so distorted that recovery of a transmit clock or transmit data from the received pulse becomes substantially difficult.
An additional problem encountered in European telephone systems involves the use of a Network Termination Basic Access (NTBA) device, used as an interface between the residential customer premises and Integrated Services Digital Network (ISDN)-based signals sent and received by a central office of the public switched telephone network. In particular, European-based telephone systems typically use a private branch exchange (PBX), coupled to the customer premises end of the NTBA device, to interconnect a plurality of analog telephone devices via respective twisted pair telephone wire for transmission of analog telephone signals carrying connection voice information. Hence, analog telephones within a customer premises will be wired in a star-type configuration by the private branch exchange. However, the telephone switch within the PBX is designed for transfer of analog telephone signals below 4 kHz, preventing the transfer of network data signals at the higher frequencies associated with one megabit per second or ten megabit per second data transmission rates.
There is a need for an arrangement for interconnecting computer end stations in a home telephone network where each telephone line pair is connected to a private branch exchange for communication of analog telephone signals.
There is also a need for an arrangement for implementing home computer networks in European-based systems using private branch exchanges for residential telephony services, with minimal modification to the existing customer premises. There is also a need for an arrangement that enables implementation of a home network for transmission of network data signals in customer premises having star-organized PBX systems.
These and other needs are obtained by the present invention, where a high-pass filter is connected between the telephone line pairs connected to the private branch exchange, enabling transmission of network data signals between the telephone line pairs for respective connected end stations.
According to one aspect of the present invention, a method is provided of interconnecting first and second computer end stations, connected to respective first and second telephone line pairs in a home telephone network wherein each of the telephone line pairs has a corresponding analog port connection to a private branch exchange (PBX), the PBX configured for communication of analog telephone signals on at least one of the first and second telephone line pairs. The method includes connecting a high pass filter between the first and second telephone line pairs, and transmitting network data signals, having frequencies substantially higher than the analog telephone signals, between the first and second computer end stations via the high pass filter. Hence, the high pass filter enables the network data signals to bypass the PBX circuitry, without interfering with the analog telephone signals.
According to another aspect of the present invention, a computer network includes first and second end stations, first and second twisted pair telephone wiring having first ends coupled to the first and second end stations, respectively, a private branch exchange coupling second ends of the first and second twisted pair telephone wiring and configured for communication of analog telephone signals on at least one of the first and second twisted pair telephone wiring, and a high pass circuit. The high pass circuit is coupled between the first and second twisted pair telephone wiring, for transmission of network data signals, having frequencies substantially higher than the analog telephone signals, between the first and second end stations.
Additional advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.